3D printing is now widely used in aerospace, healthcare, energy, automotive and other industries. Metal printing, in particular, is the fastest growing sector, yet its development presents ...scientific, technological and economic challenges that must be understood and addressed.
Additive manufacturing enables the printing of metallic parts, such as customized implants for patients, durable single-crystal parts for use in harsh environments, and the printing of parts with ...site-specific chemical compositions and properties from 3D designs. However, the selection of alloys, printing processes and process variables results in an exceptional diversity of microstructures, properties and defects that affect the serviceability of the printed parts. Control of these attributes using the rich knowledge base of metallurgy remains a challenge because of the complexity of the printing process. Transforming 3D designs created in the virtual world into high-quality products in the physical world needs a new methodology not commonly used in traditional manufacturing. Rapidly developing powerful digital tools such as mechanistic models and machine learning, when combined with the knowledge base of metallurgy, have the potential to shape the future of metal printing. Starting from product design to process planning and process monitoring and control, these tools can help improve microstructure and properties, mitigate defects, automate part inspection and accelerate part qualification. Here, we examine advances in metal printing focusing on metallurgy, as well as the use of mechanistic models and machine learning and the role they play in the expansion of the additive manufacturing of metals.Several key industries routinely use metal printing to make complex parts that are difficult to produce by conventional manufacturing. Here, we show that a synergistic combination of metallurgy, mechanistic models and machine learning is driving the continued growth of metal printing.
Since its inception, significant progress has been made in understanding additive manufacturing (AM) processes and the structure and properties of the fabricated metallic components. Because the ...field is rapidly evolving, a periodic critical assessment of our understanding is useful and this paper seeks to address this need. It covers the emerging research on AM of metallic materials and provides a comprehensive overview of the physical processes and the underlying science of metallurgical structure and properties of the deposited parts. The uniqueness of this review includes substantive discussions on refractory alloys, precious metals and compositionally graded alloys, a succinct comparison of AM with welding and a critical examination of the printability of various engineering alloys based on experiments and theory. An assessment of the status of the field, the gaps in the scientific understanding and the research needs for the expansion of AM of metallic components are provided.
The mathematical model of the solid oxide fuel cell (SOFC) is presented. The new approach for modeling the voltage of SOFC is proposed. Electrochemical, thermal, electrical, and flow parameters are ...collected in the 0D mathematical model. The aim was to combine all cell working conditions in as a low number of factors as possible and to have the factors relatively easy to determine. A validation process for various experimental data was made and adequate results are shown. The presented model was validated for various fuel mixtures in relatively wide ranges of parameters as well as for various cell design parameters (e.g. electrolyte thickness, anode porosity, etc.). A distinction is made between the “design‐point” and “off‐design operation”.
Electron beam welding (EBW) of two important engineering alloys, Ti-6Al-4V and 21Cr-6Ni-9Mn, was studied experimentally and theoretically. The temperatures at several monitoring locations in the ...specimens were measured as a function of time during welding and the cross-sections of the welds were examined by optical microscopy. The theoretical research involved numerical simulation of heat transfer and fluid flow during EBW. The model output included temperature and velocity fields, fusion zone geometry and temperature versus time results. The numerically computed fusion zone geometry and the temperature versus time plots were compared with the corresponding experimentally determined values for each weld. Both the experimental and the modelling results were compared with the corresponding results for the keyhole mode laser beam welding (LBW).
Electrochemical, thermal, electrical and flow parameters of a Molten Carbonate Fuel Cell (MCFC) are organized in a reduced order model, which is a 0-D mathematical model. The aim was to simulate ...different fuel cell working conditions taking into consideration a reduced number of parameters.
The reduced order model for an MCFC fed by syngas is formulated and implemented in Matlab.
A validation process for experimental data of the MCFC was made for some fuel and oxidant mixtures and adequate results are shown. The maximum percentage error ranges between 3.7% and 5.4% in the various considered cases.
At the anode, the direct internal water gas shift chemical reaction and the electrochemical consumption of carbon monoxide in addition to electrochemical consumption of hydrogen are considered. The ratio between the molar flows of carbon monoxide and hydrogen electrochemically consumed is a function of average rates of the electrochemical reactions and influences fuel cell performance. Furthermore, the simulation model is used to estimate the fuel cell performance varying the above-mentioned ratio. Acting on this ratio the performances of and MCFC fed by syngas and hydrogen could become comparable.
•A calculation code (CC) of an MCFC fed by syngas is set up in Matlab environment.•The CC was experimentally validated by the authors for some fuel and oxidant gases.•The ratio of CO and H2 molar flows electrochemically reacted, q, is considered.•The parameter q is a function of CO and H2 electrochemical reactions average rates.•The CC is used to estimate the fuel cell performance varying parameter q.
This paper demonstrates the benefits of using a metallic foam support within molten carbonate fuel cell (MCFC) cathodes. A state-of-the-art fabrication process based on tape casting has been ...developed to produce microporous electrodes with a nickel foam scaffold. Surfactant was added to control the depth to which the slurry infiltrated the foam. New cathodes were used as an alternative to the traditional cathode in the single cell assembly and were tested for power density. Mechanical properties were compared with the current state-of-the-art. The results show that the use of metallic foams for high temperature fuel cell electrodes is beneficial from the technological point of view, especially in larger scale production. It was also found that the resultant continuous metallic structure of the microporous electrodes delivered a slight enhancement to fuel cell power density.
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•Metallic foam-supported electrodes for molten carbonate fuel cells were fabricated and characterized.•The new electrodes exhibit superior mechanical strength and flexibility with increased power density.•The proposed innovation also facilitates the manufacturing and assembly of molten carbonate fuel cells.
In this study, the effect of microstructure of porous nickel electrode on the performance of high temperature fuel cell is investigated and presented based on a molten carbonate fuel cell (MCFC) ...cathode. The cathode materials are fabricated from slurry consisting of nickel powder and polymeric binder/solvent mixture, using the tape casting method. The final pore structure is shaped through modifying the slurry composition - with or without the addition of porogen(s). The manufactured materials are extensively characterized by various techniques involving: micro-computed tomography (micro-XCT), scanning electron microscopy (SEM), mercury porosimetry, BET and Archimedes method. Tomographic images are also analyzed and quantified to reveal the evolution of pore space due to nickel in situ oxidation to NiO, and infiltration by the electrolyte. Single-cell performance tests are carried out under MCFC operation conditions to estimate the performance of the manufactured materials. It is found that the multi-modal microstructure of MCFC cathode results in a significant enhancement of the power density generated by the reference cell. To give greater insight into the understanding of the effect of microstructure on the properties of the cathode, a model based on 3D tomography image transformation is proposed.
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•Molten carbonate fuel cell cathodes with various microstructures are fabricated.•Materials are extensively characterized before and after operation.•The evolution of pore space due to oxidation and infiltration is described.•Multi-modal microstructure results in doubling the power density of the fuel cell.
This paper presents recent activities of the IAHE Nuclear Hydrogen Division and associated research advances in Canada, China, France, Germany, Poland, and Romania on programs and major initiatives ...on large-scale hydrogen production and utilization. Germany and France have made significant advances in high temperature steam electrolysis (HTSE). Germany is going to demonstrate a 3-kW steam electrolyzer and 100-kW Hybrid Sulfur Cycle powered by solar energy soon. France operated several HTSE 25-cell stacks at various operating points. Recently, a HTSE packaged system has been built, containing this 25-cell stack and other Balance of Plant components. At 700 °C, this system produces 1.2 Nm3/h of H2 with a total electrical consumption of 3.9 kWh/Nm3, achieving 92% of efficiency (electrical consumption of the system vs HHV of the produced hydrogen). It demonstrates that a 150 °C heat source temperature is sufficient for the steam generation, and that a slightly exothermic operating mode of the stack is sufficient to preheat the inlet gas up to 700 °C and compensate the heat losses of the system. China has also made significant progress in developing the HTSE process at a hydrogen production rate of 105 dm3/h and the thermochemical Sulfur–Iodine (SI) cycle at the rate of 60 dm3/h, which already achieved the goal of China's HTR-PM Demonstration Nuclear Power Plant Project. The components and facilities were developed and tested in Tsinghua University. Romania is collaborating with Canada on nuclear hydrogen production with the thermochemical Cu–Cl cycle. The individual unit operations of the Cu–Cl cycle have been verified experimentally. Research on integration of a laboratory scale system to produce 3 kg of hydrogen per day is underway at the University of Ontario Institute of Technology in Oshawa, Ontario. Poland has developed advanced simulation capabilities for Solid Oxide Fuel/Electrolysis Cells for hydrogen peak energy storage as well as laboratory scale experiments focused on solid oxide and molten carbonate fuel cells. This paper presents a review of activities of members of the IAHE Nuclear Hydrogen Division in these six countries.
•Recent advances in large scale hydrogen production for 6 countries.•Results from HTSE packaged system 25-cell stack in France reported.•China's advanced demonstration of thermochemical 60 dm3/h SI cycle.•Germany's solar energy powered 100-kW Hybrid Sulfur Cycle reported.•Advances in lab scale system to produce 3 kg of H2 per day in Canada reported.
G3-G9 dendritic polyelectrolytes accompanied by counterions are investigated using the Poisson-Boltzmann-Flory theory. Within this approach we solve numerically the Poisson-Boltzmann equation for the ...mean electrostatic potential and minimize the Poisson-Boltzmann-Flory free energy with respect to the size of the molecules. Such a scheme enables us to inspect the conformational and electrostatic properties of the dendrimers in equilibrium based on their response to varying the dendrimer generation. The calculations indicate that the G3-G6 dendrimers exist in the polyelectrolyte regime where absorption of counterions into the volume of the molecules is minor. Trapping of ions in the interior region becomes significant for the G7-G9 dendrimers and signals the emergence of the osmotic regime. We find that the behavior of the dendritic polyelectrolytes corresponds with the degree of ion trapping. In particular, in both regimes the polyelectrolytes are swollen as compared to their neutral counterparts and the expansion factor is maximal at the crossover generation G7.
The conformational and electrostatic properties of dendritic polyelectrolytes accompanied by counterions are investigated using the Poisson-Boltzmann-Flory theory.
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